The invention relates to a portable telephone, and more particularly to a portable telephone comprising a slidable cover.
There is a tendency nowadays for portable radio telephones to become increasingly lightweight and compact. However, as overall dimensions decrease, it has to be borne in mind that there is a critical minimum dimensional constraint on the separation of the microphone and the earpiece imposed by the distance between the ear and the mouth of the human head, typically around 15 centimetres.
This is addressed in the Nokia 8110 phone, which is depicted in FIG. 1 of the accompanying drawings. This phone 1 comprises a main body 3 and a cover 2 which houses the microphone. When the telephone is not in use, the cover 2 is slid to its closed position as shown in FIG. 1a, the overall length of the telephone then only being approximately 14 centimetres. When in use, the cover is slid into an open position thereby establishing the optimum space in between the earphone and the microphone for convenient use.
As can be seen from FIGS. 1b and 1c, the cover 2 has a sidewall 16 in each side which terminates in an inwardly directed flange 17 which extends in parallel with the transverse direction of the telephone. Correspondingly, the telephone housing 3 is formed with guide tracks 35. When the user applies pressure to the cover to move it between the open and closed positions, these guide flanges move along the guide rails 35.
Whilst this sliding arrangement of the guide rails 35 and flange 17 work well, the aesthetic and tactile qualities of the sliding arrangement could be further improved. One particular weakness is the fact that the user needs to apply more force when initially moving the cover from its closed position to move a certain distance than it does from a partly open position to move it the same distance.
GB 2310560 which relates to an invention implemented in the Nokia 8110, suggests replacing the flanges 17 which run along the length of the cover with discrete guide pins positioned along the length of the cover. However, such an implementation would still have the aforementioned weaknesses.
According to the present invention there is provided a radiotelephone comprising a first part; a second part arranged for relative sliding movement with the first part, between a closed position in which the first and second parts at least partially overlap and an open position; and guide means for guiding the relative sliding movement, the guide means comprising a guide track on the first part and a guide rail on the second part; wherein the guide rail extends along a portion of the guide track when the second part is in the open and closed position; and the force between the two parts is substantially constant over a range of positions along the guide track.
Such a radio telephone has a substantially constant friction sliding arrangement, which provides a tactile improvement for the user. That is, he can apply substantially the same force to one of the parts to move it a certain distance relative to the other, irrespective of its starting position.
Preferably the first part of the radio telephone is its body and the second part its cover. This provides an aesthetic improvement over conventional slide phones, as guide rails are no longer required down the side of the phone.
Preferably, the guide rail is dimensioned to prevent substantial relative pivoting of the first part about it. Moreover, the width of the guide rail is optionally substantially the same as the width of the guide track. This enables a constant distance to be maintained between the two parts.
The guide rail may comprise a single short flange, or alternatively two pins. It is preferable if the two pins are positioned again to prevent substantial relative pivoting of the parts, and thus to prevent any flapping of the ends of the parts remote from the pins.
Preferably, the pins have curved ends (e.g. hemispherical) as these provide a smaller surface contact area so reducing friction further. Moreover, they have the additional advantage of being able to be readily inserted in the guide tracks should the parts become separated.
Suitably, the guide rail and guide tracks have surfaces made of materials with low friction properties, and yet which are durable to repetitive sliding contact. Preferably, the guide rail is composed of metal and the guide track is composed of plastics.
The guide track may be shaped to angle one part with respect to the other such that, for example, a microphone in a cover part of the telephone may be positioned closer to the user""s mouth.
The guide track may be a groove. This eliminates the need for end stops and thus reduces the number of parts required for the sliding mechanism.
The telephone may comprise one or more latches for latching the first and second parts at certain positions. For example, it may comprise a latch for latching the parts in the closed position and/or open position and/or any intermediate position (for example an intermediate position at which only the function keys are revealed). The latch may comprise a resilient arm with a protection on one part of the telephone and a corresponding protrusion, for interfering contact with the projection, on the second part.
The telephone may also comprise further features such as a catching mechanism which ensures that when in the closed position the surfaces of the first and second parts of the telephone are in alignment.